Field of the Invention
The present invention relates in general to internal combustion engines comprising two inlet valves per cylinder, actuated by a single common rocker, the inlet ports formed jointly by the pair of valves and their seats communicating via an induction duct formed in the cylinder head with an external source of gaseous fluid.
Diesel engines comprising two air inlet valves per cylinder are already known, wherein the pair of inlet valves are actuated simultaneously by a single rocker common to both inlet valves. In an engine of this character, the pair of inlet valves communicates via a common induction passage formed in the cylinder head with an air induction manifold either cast integrally with the cylinder head or disposed externally of the cylinder head and connected thereto.
On the other hand, compound Diesel-gas engines are also known which comprise two inlet valves each connected via a separate induction duct or passage to a separate source of fluid, such as an air source and a source of gaseous fuel, respectively. However, in this type of engine the pair of inlet valves has generally different diameters, for example the air induction valve has a relatively great diameter and the gas induction valve has a smaller diameter. Moreover, in engines of this type the two inlet valves for the air and gas respectively are actuated by separate, different rockers.
Besides, internal combustion engines are also known which operate only on gaseous fuel. As a rule, these engines comprise only one inlet valve per cylinder, the inlet port being connected to an induction manifold. In this case, the air/fuel mixture is formed either upstream of the induction manifold or within this manifold by means of an auxiliary valve through which gas can be injected into said manifold.
From the foregoing, it is clear that for the three types of engines broadly described hereinabove different cylinder heads and also different gears or mechanisms for actuating the various inlet valves must be contemplated.